What is this for?

[ToneChaser]

Hi guys,

Dad had an old amp sitting around he hadn't played in years. Its an Ampeg Gemini 1. He thinks its a 1966. It seems to have the original tubes and most likely original caps, etc...

I'm really enjoying it, but its got a terrible vibration or possible electrical component related distortion, with certain frequencies. I took the back off and found this spring just screwed inside the cabinet. What is that for? Its not wired to anything. I took it out, but the vibration continues. I haven't dived into the rest of the amp yet.

Any advice on common things to look out for with these amps? Services you recommend doing? Anyone have a link to an old factory service manual or anything like that?

Other than the vibration, I'm enjoying the amp's sound. Its certainly different from my tweed deluxe

   
   

[Hangman]

Hello!  Welcome to the VintageAmpeg.com Forums! Thanks for registering.

The Gemini 1 is one of my favorite amps.  I have a 1968 G12 which is the same circuit but in a cabinet that looks more like the V4 or SVT.  (blue line era)

The spring in the back was there to hold the footswitch see my image below:
   

There isn't really a service manual, but you can find the Schematics on this website under "DOCS"

At this point if the electrolytic capacitors have not been replaced you really need to replace them.  I would do that ASAP.  Ampeg used high quality caps,  but this amp is over 50 years old! The last thing you want is for one of those caps to blow up.  I've had to clean up the mess that leaves behind,  not fun and very toxic. 

Find a tech that really cares about keeping the amp as original as possible.  Its really easy to start cutting holes for new caps, or using silicone to hold a wad of caps in place... or taking the shotgun approach (just replacing all of the caps) but finding someone that will really do a good job is hard.

can you describe the vibration?  does it sound like a light rattle?   the 7199 tube does tend to have a slight microphonic rattle (as many pentodes do)

best regards,
-Steve